High speed ink jet printing employs multiple nozzles, each producing a stream of drops that are selectively deflected to designated data points on a recording surface. Usually, the plurality of nozzles is arranged in a row transverse to the relatively moving recording surface and each nozzle has its own drop charging ring and its own set of deflection plates to appropriately direct the drop to their respective data points. Unwanted drops are directed to a catcher or gutter for accumulation and possible reuse.
The arrangement shown in U.S. Pat. No. 3,786,517 to K. A. Krause, shows a typical transverse orientation of a nozzle plurality. The number of nozzles and their controls is optional and can be the number required to record a full line on the record surface. Many deflection levels are necessary to record with the resolution desired. These numerous deflection levels add greatly to the control signal complexity because of compensation to counteract adverse effects of charge interaction and aerodynamics.
A somewhat similar arrangement is shown in U.S. Pat. No. 3,739,395 to K. O. King in which a plurality of transverse rows are used, each offset slightly from the preceding in order to cover all data points along the width of the recording surface. The streams can be deflected in two orthogonal directions; each nozzle in a row has an individual pair of deflection electrodes and all of the nozzles in a row have a pair of common deflection electrodes at right angles with respect to the individual pairs. Deflection by the common electrode is in the direction of motion.
In both of the foregoing patents there is difficulty in making the necessary structure sufficiently small to cover all desired data points on a recording surface. In addition, the control of the drop charging and deflection signals becomes exceedingly complex.
Another transverse arrangement of nozzles is shown in U.S. Pat. No. 3,871,004 and uses selectively operable deflection electrodes to move ink drops a single level of deflection above or below the nozzle with respect to motion of the nozzle row. The drops are generated only on demand and are not selectively charged, but are deflected by the presence of a switched attracting field. Each electrode is discretely contoured adjacent each nozzle.
A different approach has been to increase the number of nozzles in the transverse row and provide one nozzle per line of data points so that the control is binary with the drops being either allowed to reach the recording surface or deflected to a gutter. This arrangement is illustrated in U.S. Pat. No. 3,373,437 to R. G. Sweet et al. Such an arrangement has not been acceptable, however, because the nozzles cannot be placed sufficiently close together to meet the resolution requirements. Quality printing requires approximately 240 pels or print elements per inch or more.
Another proposed solution is that described in a U.S. patent Application entitled "Multi-Nozzle Ink Jet Print Head Apparatus," Ser. No. 671,920, filed Mar. 29, 1976, by K. A. Krause and assigned to the assignee of the present application. In that application, multiple rows of nozzles are inclined with respect to the relative document-to-print head motion so that drops from a series of nozzles are able to impact the recording surface in an overlapping or contacting manner to produce a line segement. The inclination of the nozzle rows is relatively steep because the nozzles, due to structural limitations, cannot be placed sufficiently close to one another. In order to produce a linear mark extending across the width of the recording surface, numerous nozzle series must be accurately positioned and controlled. One nozzle is needed for each row of print elements or data points in the printed line.
Another proposed solution has been disclosed in a U.S. patent application entitled "Multi-Nozzle Ink Jet Printer And Method of Printing," Ser. No. 646,130, filed Jan. 2, 1976 by D. F. Jensen, et al., and assigned to the assignee of the present application. In that application, a series of ink jet nozzles are arranged in a row inclined to the relative motion between the print head and recording surface. The drops in the stream from each nozzle are selectively controlled to impact the recording surface at different levels of deflection. Each nozzle is capable of printing a plurality of lines of data points, and each nozzle has its own deflection means. When recording occurs during continuous relative motion, each deflection means must be individually tailored to lead the approaching desired data point to accurately place the ultimate mark.
The known ink jet printers require either individual deflection devices for each ink stream, are limited to a single level of deflection, or can deflect only along the direction of relative motion. In addition, these printers either do not have to consider a compensation for relative motion between the ink streams and recording surface, or they have adjustments in the structure or signals individual to each stream.
It is accordingly a primary object of this invention to provide an arrangement of common planar electrodes capable of deflecting the ink streams of a plurality of nozzles each to a plurality of levels of deflection during continuous relative motion with respect to the recording surface.
Another object of this invention is to provide an arrangement of a plurality of ink jet nozzles and charging means with a pair of common electrodes capable of deflecting the drops in each nozzle stream to a plurality of levels of deflection which includes compensation via electrode orientation for relative motion between the nozzles and the recording surface.
Yet another object of this invention is to provide a method of determining the inclination of a row of nozzles and deflection electrodes with respect to a recording surface which includes compensation by a common electrode adjustment for relative motion of the nozzles and surface and permits selection of different matrical arrangements of drop placement on the surface.
A still further object of this invention is to provide an electrostatically deflected ink jet recording arrangement for a plurality of nozzles aligned in one or more parallel rows inclined with respect to the relative motion of the recording surface, each nozzle of which can record a plurality of parallel rows of drops at predetermined data points on an orthogonal grid on the recording surface.